Thermoplastic resin composition

ABSTRACT

A thermoplastic resin composition of the present invention comprises: (A) 100 parts by weight of a thermoplastic resin comprising (A1) a rubber-modified aromatic vinyl-based graft copolymer, (A2) an aromatic vinyl-based copolymer resin having a flow index of about 5 g/10 min to about 8 g/10 min as measured by the ASTM D 1238 standard, and (A3) an α-methylstyrene copolymer; and (B) about 0.1 to about 10 parts by weight of zinc oxide, wherein the zinc oxide has a size ratio (B/A) of peak A in the region of 370 nm to 390 nm to peak B in the region of 450 nm to 600 nm of about 0.01 to about 1 in photoluminescence measurement, and has a BET surface area of about 10 m 2 /g or less as measured by a BET analyzer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of InternationalApplication No. PCT/KR2017/015150, filed Dec. 20, 2017, which publishedas WO 2018/124614 on Jul. 5, 2018; Korean Patent Application No.10-2016-0184168, filed in the Korean Intellectual Property Office onDec. 30, 2016; and Korean Patent Application No. 10-2017-0149823, filedin the Korean Intellectual Property Office on Nov. 10, 2017, the entiredisclosure of each of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a thermoplastic resin composition. Moreparticularly, the present invention relates to a thermoplastic resincomposition that exhibits good balance between low odor, impactstrength, creep resistance, fluidity, heat resistance, and antibacterialproperties.

BACKGROUND ART

As a thermoplastic resin, a rubber-modified aromatic vinyl copolymerresin such as an acrylonitrile-butadiene-styrene copolymer resin (ABSresin) has good properties in terms of mechanical properties,processability, external appearance, and the like, and is broadly usedas interior/exterior materials for electric/electronic products,automobiles, buildings, and the like.

In particular, despite low manufacturing costs and good moldability tobe used as 3D printing materials, the rubber-modified aromatic vinylcopolymer resin has a disadvantage of generating a strong plastic odorduring or after molding due to generation of an excess of out-gas(unreacted volatile organic compounds).

Moreover, when such resins are used for applications entailing physicalcontact with the body, such as medical equipment, toys, food containers,and the like, the resins are required to have antibacterial properties.In particular, in application to materials for OA, it is important forthe resins to have creep resistance together with antibacterialproperties and low odor.

Conventionally, hydrogenation has been proposed to achieve a deodoranteffect. However, this method is difficult to apply to an actual processand requires additional facility costs due to difficulty in applicationto existing process facilities.

In addition, although an aromatic vinyl copolymer having a highmolecular weight may be used in order to improve creep resistance of theresin, this method has a problem of deterioration in fluidity.

Therefore, there is a need for a thermoplastic resin composition thatexhibits good balance between low odor, impact strength, creepresistance, heat resistance, fluidity, and antibacterial properties.

The background technique of the present invention is disclosed in KoreanPatent Laid-open Publication No. 2016-0001572 and the like.

DISCLOSURE Technical Problem

It is an object of the present invention to provide a thermoplasticresin composition exhibiting good balance between low odor, impactstrength, creep resistance, heat resistance, fluidity, and antibacterialproperties.

It is another object of the present invention to provide a thermoplasticresin composition exhibiting good flame retardancy without using aseparate flame retardant.

The above and other objects of the present invention can be achieved bythe present invention described below.

Technical Solution

One aspect of the present invention relates to a thermoplastic resincomposition. The thermoplastic resin composition may include: 100 partsby weight of (A) a thermoplastic resin including (A1) a rubber-modifiedaromatic vinyl graft copolymer; (A2) an aromatic vinyl copolymer resinhaving a melt index (MI) of about 5 g/10 min to about 8 g/10 min, asmeasured in accordance with ASTM D 1238; and (A3) an α-methylstyrenecopolymer; about 0.1 parts by weight to about 10 parts by weight of (B)zinc oxide, wherein the zinc oxide has a peak intensity ratio (B/A) ofabout 0.01 to about 1, where A indicates a peak in the wavelength rangeof 370 nm to 390 nm and B indicates a peak in the wavelength range of450 nm to 600 nm in photoluminescence measurement and a BET surface areaof about 10 m²/g or less, as measured using a BET analyzer.

In one embodiment, the (A2) aromatic vinyl copolymer resin may have aweight average molecular weight of about 85,000 g/mol to about 150,000g/mol.

In one embodiment, the (A3) α-methylstyrene copolymer may be a copolymerof about 65 wt % to about 80 wt % of α-methylstyrene and about 20 wt %to about 35 wt % of acrylonitrile.

In one embodiment, the (A3) α-methylstyrene copolymer may have a weightaverage molecular weight of about 130,000 g/mol to about 180,000 g/mol.

In one embodiment, the thermoplastic resin composition may satisfy thefollowing Relation 1.M _(A2) <M _(A3),  [Relation 1]

where M_(A2) is the weight average molecular weight of the (A2) aromaticvinyl copolymer resin and M_(A3) is the weight average molecular weightof the (A3) α-methylstyrene copolymer.

In one embodiment, the (A2) aromatic vinyl copolymer resin and the (A3)α-methylstyrene copolymer may be present in a weight ratio ((A2):(A3))of about 5:1 to about 15:1.

In one embodiment, the (A) thermoplastic resin may include about 20 wt %to about 45 wt % of the (A1) rubber-modified aromatic vinyl graftcopolymer; about 40 wt % to about 75 wt % of the (A2) aromatic vinylcopolymer resin; and about 3 wt % to about 15 wt % of the (A3)α-methylstyrene copolymer.

In one embodiment, the zinc oxide may have an average particle diameter(D50) of about 0.2 μm to about 3 μm.

In one embodiment, the zinc oxide may have a peak position (2θ) in therange of 35° to 370 in X-ray diffraction (XRD) analysis and acrystallite size of about 1,000 Å to about 2,000 Å, as calculated byEquation 2.

$\begin{matrix}{{{{Crystallite}\mspace{14mu}{size}\mspace{14mu}(D)} = \frac{K\lambda}{\beta cos\theta}},} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

where K is a shape factor, λ is an X-ray wavelength, β is an FWHM value(degree) of an X-ray diffraction peak, and θ is a peak position degree.

In one embodiment, the zinc oxide may have a peak intensity ratio (B/A)of about 0.01 to about 0.5, where A indicates a peak in the wavelengthrange of 370 nm to 390 nm and B indicates a peak in the wavelength rangeof 450 nm to 600 nm in measurement of photoluminescence.

In one embodiment, the (A3) α-methylstyrene copolymer and the (B) zincoxide may be present in a weight ratio of about 1.5:1 to about 15:1.

In one embodiment, the thermoplastic resin composition may have a totalvolatile organic compound (TVOC) of 1,780 Area/g or less at 120° C. for5 hours, an impact strength of about 18 kgf·cm/cm or more as measured ona ⅛″ thick specimen in accordance with ASTMD256, an antibacterialactivity against Staphylococcus aureus of about 2.0 to about 7.0 and anantibacterial activity against Escherichia coli of about 2.0 to about7.5, as measured on 5 cm×5 cm specimens inoculated with Staphylococcusaureus and Escherichia coli, respectively, in accordance with JIS Z 2801and calculated according to Equation 3.Antibacterial activity=log(M1/M2),  [Equation 3]

where M1 is the number of bacteria as measured on a blank specimen afterincubation under conditions of 35° C. and 90% RH for 24 hours, and M2 isthe number of bacteria as measured on a specimen of the foam afterincubation under conditions of 35° C. and 90% RH for 24 hours.

Another aspect of the present invention relates to a molded articleformed of the thermoplastic resin composition as set forth above.

Advantageous Effects

The present invention provides a thermoplastic resin composition thathas good balance between low odor, impact strength, creep resistance,heat resistance, fluidity and antibacterial properties, and exhibitsgood flame retardancy without using a separate flame retardant.

Best Mode

(A) Thermoplastic Resin

The thermoplastic resin according to the present invention includes (A1)a rubber-modified aromatic vinyl graft copolymer; (A2) an aromatic vinylcopolymer resin having a melt index of about 5 g/10 min to about 8 g/10min, as measured in accordance with ASTM D 1238; and (A3) anα-methylstyrene copolymer.

(A1) Rubber-Modified Aromatic Vinyl Graft Copolymer

The rubber-modified aromatic vinyl graft copolymer according to oneembodiment of the invention may be obtained through graftcopolymerization of an aromatic vinyl monomer and a monomercopolymerizable with the aromatic vinyl monomer to a rubber polymer.

In some embodiments, the rubber-modified vinyl graft copolymer may beobtained by adding the aromatic vinyl monomer and the monomercopolymerizable with the aromatic vinyl monomer to the rubber polymer,followed by polymerization, which may be carried out by any knownpolymerization method, such as emulsion polymerization, suspensionpolymerization, bulk polymerization, and the like.

In some embodiments, the rubber polymer may include diene rubbers, suchas polybutadiene, poly(styrene-butadiene), andpoly(acrylonitrile-butadiene); saturated rubbers obtained by addinghydrogen to the diene rubbers; isoprene rubbers; acrylic rubbers such aspoly(butyl acrylate); and ethylene-propylene-diene monomer terpolymer(EPDM). These may be used alone or as a mixture thereof. For example,the rubber polymer may be diene rubbers, specifically butadiene rubbers.The rubber polymer may be present in an amount of about 5 wt % to about65 wt %, specifically about 10 wt % to about 60 wt %, more specificallyabout 20 wt % to about 50 wt %, for example, 20 wt %, 21 wt %, 22 wt %,23 wt %, 24 wt %, 25 wt %, 26 wt %, 27 wt %, 28 wt %, 29 wt %, 30 wt %,31 wt %, 32 wt %, 33 wt %, 34 wt %, 35 wt %, 36 wt %, 37 wt %, 38 wt %,39 wt %, 40 wt %, 41 wt %, 42 wt %, 43 wt %, 44 wt %, 45 wt %, 46 wt %,47 wt %, 48 wt %, 49 wt %, or 50 wt %, based on 100 wt % of therubber-modified aromatic vinyl graft copolymer. Within this range, thethermoplastic resin composition can exhibit good impact resistance andmechanical properties.

In addition, the rubber polymer (rubber particle) may have an averageparticle diameter (Z-average) of about 0.1 μm to about 1 μm,specifically about 0.15 m to about 0.5 μm, more specifically about 0.20μm to about 0.35 μm, for example, 0.20 μm, 0.21 μm, 0.22 μm, 0.23 μm,0.24 μm, 0.25 μm, 0.26 μm, 0.27 μm, 0.28 μm, 0.29 μm, 0.30 μm, 0.31 μm,0.32 μm, 0.33 μm, 0.34 μm, or 0.35 μm. Within this range, thethermoplastic resin composition can have good properties in terms ofimpact resistance, external appearance, and the like.

In some embodiments, the aromatic vinyl monomer is a monomercopolymerizable with the rubber copolymer and may include, for example,styrene, α-methyl styrene, p-methyl styrene, p-t-butyl styrene,ethylstyrene, vinylxylene, monochlorostyrene, dichlorostyrene,dibromostyrene, and vinyl naphthalene, without being limited thereto.These may be used alone or as a mixture thereof. The aromatic vinylmonomer may be present in an amount of about 15 wt % to about 94 wt %,specifically about 20 wt % to about 80 wt %, more specifically about 30wt % to about 60 wt %, for example, 30 wt %, 31 wt %, 32 wt %, 33 wt %,34 wt %, 35 wt %, 36 wt %, 37 wt %, 38 wt %, 39 wt %, 40 wt %, 41 wt %,42 wt %, 43 wt %, 44 wt %, 45 wt %, 46 wt %, 47 wt %, 48 wt %, 49 wt %,50 wt %, 51 wt %, 52 wt %, 53 wt %, 54 wt %, 55 wt %, 56 wt %, 57 wt %,58 wt %, 59 wt %, or 60 wt %, based on 100 wt % of the rubber-modifiedaromatic vinyl graft copolymer. Within this range, the thermoplasticresin composition can exhibit good properties in terms of fatigueresistance, impact resistance, mechanical properties, and the like.

In some embodiments, the monomer copolymerizable with the aromatic vinylmonomer may include for example, a vinyl cyanide compound, such asacrylonitrile, methacrylonitrile, ethacrylonitrile, phenylacrylonitrile, α-chloroacrylonitrile, and fumaronitrile, acrylic acidand an alky ester thereof, maleic anhydride, N-substituted maleimide,and the like. These may be used alone or as a mixture thereof.Specifically, the monomer copolymerizable with the aromatic vinylmonomer may be selected from among acrylonitrile, methyl (meth)acrylate,and combinations thereof. The monomer copolymerizable with the aromaticvinyl monomer may be present in an amount of about 1 wt % to about 50 wt%, specifically about 5 wt % to about 45 wt %, more specifically about10 wt % to about 30 wt %, for example, 10 wt %, 11 wt %, 12 wt %, 13 wt%, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, 19 wt %, 20 wt %, 21 wt%, 22 wt %, 23 wt %, 24 wt %, 25 wt %, 26 wt %, 27 wt %, 28 wt %, 29 wt%, or 30 wt %, based on 100 wt % of the rubber-modified aromatic vinylgraft copolymer. Within this range, the thermoplastic resin compositioncan have good properties in terms of impact resistance, fluidity,external appearance, and the like.

In some embodiments, the rubber-modified vinyl graft copolymer mayinclude a g-ABS copolymer obtained by grafting a styrene monomer (as anaromatic vinyl compound) and an acrylonitrile monomer (as a vinylcyanide compound) to a butadiene-based rubber polymer and a g-MBScopolymer obtained by grafting a styrene monomer (as an aromatic vinylcompound) and methyl methacrylate (as a monomer copolymerizable with thearomatic vinyl compound) to a butadiene-based rubber polymer, withoutbeing limited thereto.

In some embodiments, the rubber-modified aromatic vinyl graft copolymermay be present in an amount of about 20 wt % to about 45 wt %,specifically about 25 wt % to about 40 wt %, for example, 25 wt %, 26 wt%, 27 wt %, 28 wt %, 29 wt %, 30 wt %, 31 wt %, 32 wt %, 33 wt %, 34 wt%, 35 wt %, 36 wt %, 37 wt %, 38 wt %, 39 wt %, or 40 wt %, based on 100wt % of the thermoplastic resin. Within this range, the thermoplasticresin composition can exhibit good properties in terms of impactresistance, fluidity (formability), and the like.

(A2) Aromatic Vinyl Copolymer Resin

The aromatic vinyl copolymer resin according to the present inventionmay have a high melt index of about 5 g/10 min to about 8 g/10 min,specifically about 5 g/10 min to about 7.5 g/10 min, for example, 5 g/10min, 5.5 g/10 min, 6 g/10 min, 6.5 g/10 min, 7 g/10 min, or 7.5 g/10min, as measured using a Gottfert MI-3 in accordance with ASTM D 1238.If the aromatic vinyl copolymer resin has a melt index of greater thanabout 8 g/10 min, the thermoplastic resin composition can suffer fromdeterioration in creep resistance, and if the aromatic vinyl copolymerresin has a melt index of less than about 5 g/10 min, the thermoplasticresin composition can suffer from deterioration in injection properties.

In some embodiments, the aromatic vinyl copolymer resin may be a polymerof a monomer mixture including an aromatic vinyl monomer and a monomercopolymerizable with the aromatic vinyl monomer, such as a vinyl cyanidemonomer.

In some embodiments, the aromatic vinyl copolymer resin may be obtainedby mixing the aromatic vinyl monomer and the monomer copolymerizablewith the aromatic vinyl monomer, followed by polymerization, which maybe carried out by any known polymerization method, such as emulsionpolymerization, suspension polymerization, bulk polymerization, and thelike.

Examples of the aromatic vinyl monomer may include styrene,α-methylstyrene, p-methyl styrene, p-t-butyl styrene, ethylstyrene,vinylxylene, monochlorostyrene, dichlorostyrene, dibromostyrene, andvinyl naphthalene, without being limited thereto. These may be usedalone or as a mixture thereof. The aromatic vinyl monomer may be presentin an amount of about 50 wt % to about 90 wt %, specifically about 65 wt% to about 85 wt %, for example, 65 wt %, 66 wt %, 67 wt %, 68 wt %, 69wt %, 70 wt %, 71 wt %, 72 wt %, 73 wt %, 74 wt %, 75 wt %, 76 wt %, 77wt %, 78 wt %, 79 wt %, 80 wt %, 81 wt %, 82 wt %, 83 wt %, 84 wt %, or85 wt %, based on based on 100 wt % of the aromatic vinyl copolymerresin. Within this range, the thermoplastic resin composition canexhibit good properties in terms of impact resistance, fluidity, and thelike.

In some embodiments, the monomer copolymerizable with the aromatic vinylmonomer may be a vinyl cyanide monomer, such as acrylonitrile,methacrylonitrile, ethacrylonitrile, phenyl acrylonitrile,α-chloroacrylonitrile, fumaronitrile, and the like. These may be usedalone or as a mixture thereof. The monomer copolymerizable with thearomatic vinyl monomer may be present in an amount of about 10 wt % toabout 80 wt %, specifically about 20 wt % to about 70 wt %, morespecifically about 30 wt % to about 60 wt %, for example, 30 wt %, 31 wt%, 32 wt %, 33 wt %, 34 wt %, 35 wt %, 36 wt %, 37 wt %, 38 wt %, 39 wt%, 40 wt %, 41 wt %, 42 wt %, 43 wt %, 44 wt %, 45 wt %, 46 wt %, 47 wt%, 48 wt %, 49 wt %, 50 wt %, 51 wt %, 52 wt %, 53 wt %, 54 wt %, 55 wt%, 56 wt %, 57 wt %, 58 wt %, 59 wt %, or 60 wt %, based on 100 wt % ofthe aromatic vinyl copolymer resin. Within this range, the thermoplasticresin composition can exhibit good properties in terms of impactresistance, fluidity, and the like.

In some embodiments, the aromatic vinyl copolymer resin may have aweight average molecular weight (Mw) of about 85,000 g/mol to about150,000 g/mol, specifically about 90,000 g/mol to about 140,000 g/mol,for example, 90,000 g/mol, 95,000 g/mol, 100,000 g/mol, 105,000 g/mol,110,000 g/mol, 115,000 g/mol, 120,000 g/mol, 125,000 g/mol, 130,000g/mol, 135,000 g/mol, or 140,000 g/mol, as measured by gel permeationchromatography (GPC). Within this range, the thermoplastic resincomposition can exhibit good properties in terms of mechanical strength,formability, and the like.

In some embodiments, the aromatic vinyl copolymer resin may be presentin an amount of about 40 wt % to about 75 wt %, specifically about 50 wt% to about 70 wt %, for example, 50 wt %, 51 wt %, 52 wt %, 53 wt %, 54wt %, 55 wt %, 56 wt %, 57 wt %, 58 wt %, 59 wt %, 60 wt %, 61 wt %, 62wt %, 63 wt %, 64 wt %, 65 wt %, 66 wt %, 67 wt %, 68 wt %, 69 wt %, or70 wt %, based on 100 wt % of the thermoplastic resin. Within thisrange, the thermoplastic resin composition can exhibit good propertiesin terms of impact resistance, fluidity (formability), and the like.

(A3) α-Methylstyrene Copolymer

The α-methylstyrene copolymer according to the present invention may bea polymer of a monomer mixture including α-methylstyrene and a monomercopolymerizable with α-methylstyrene.

In some embodiments, in the α-methylstyrene copolymer, α-methylstyrenemay be present in an amount of about 65 wt % to about 80 wt %, forexample, 65 wt %, 66 wt %, 67 wt %, 68 wt %, 69 wt %, 70 wt %, 71 wt %,72 wt %, 73 wt %, 74 wt %, 75 wt %, 76 wt %, 77 wt %, 78 wt %, 79 wt %,or 80 wt %, and the copolymerizable monomer may be present in an amountof about 20 wt % to about 35 wt %, for example, 20 wt %, 21 wt %, 22 wt%, 23 wt %, 24 wt %, 25 wt %, 26 wt %, 27 wt %, 28 wt %, 29 wt %, 30 wt%, 31 wt %, 32 wt %, 33 wt %, 34 wt %, or 35 wt %. Within this range,the thermoplastic resin composition can exhibit good properties in termsof heat resistance, impact resistance, and fluidity.

The copolymerizable monomer may be a vinyl cyanide monomer, such asacrylonitrile, methacrylonitrile, ethacrylonitrile, phenylacrylonitrile, α-chloroacrylonitrile, fumaronitrile, and the like. Thesemay be used alone or as a mixture thereof.

In some embodiments, the α-methylstyrene copolymer may be prepared bymixing α-methylstyrene and the monomer copolymerizable therewith,followed by polymerization, which may be carried out by any well-knownpolymerization method, such as emulsion polymerization, suspensionpolymerization, bulk polymerization, and the like.

In some embodiments, the α-methylstyrene copolymer may have a weightaverage molecular weight (Mw) of about 130,000 g/mol to about 180,000g/mol, specifically about 135,000 g/mol to about 160,000 g/mol, forexample, 135,000 g/mol, 140,000 g/mol, 145,000 g/mol, 150,000 g/mol,155,000 g/mol, or 160,000 g/mol, as measured by GPC. Within this range,the thermoplastic resin composition exhibits good properties in terms ofmechanical strength, formability, and the like.

On the other hand, when M_(A2) indicates the weight average molecularweight of the (A2) aromatic vinyl copolymer resin and M_(A3) indicatesthe weight average molecular weight of the (A3) α-methylstyrenecopolymer, the (A2) aromatic vinyl copolymer resin and the (A3)α-methylstyrene copolymer satisfy the following Relation 1.M _(A2) <M _(A3),  [Relation 1]

where M_(A2) indicates the weight average molecular weight of the (A2)aromatic vinyl copolymer resin and M_(A3) indicates the weight averagemolecular weight of the (A3) α-methylstyrene copolymer.

In addition, the (A2) aromatic vinyl copolymer resin and the (A3)α-methylstyrene copolymer may be present in a weight ratio of about 5:1to about 15:1, for example, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1,13:1, 14:1, or 15:1. Within this range, the thermoplastic resincomposition has good creep resistance.

In some embodiments, the α-methylstyrene copolymer may be present in anamount of about 3 wt % to about 15 wt %, specifically about 5 wt % toabout 10 wt %, for example, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, or10 wt %, based on 100 wt % of the thermoplastic resin. Within thisrange, the thermoplastic resin composition can exhibit good propertiesin terms of impact resistance, fluidity (formability), and the like.

(B) Zinc Oxide

The zinc oxide according to the present invention has a peak intensityratio (B/A) of about 0.01 to about 1, specifically about 0.01 to about0.5, preferably about 0.01 to about 0.1, for example, 0.01, 0.02, 0.03,0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1, where A indicates a peak inthe wavelength range of 370 nm to 390 nm and B indicates a peak in thewavelength range of 450 nm to 600 nm in photoluminescence measurement,and a BET surface area of about 10 m²/g or less, specifically about 1m²/g to about 7 m²/g, for example, 1 m²/g, 2 m²/g, 3 m²/g, 4 m²/g, 5m²/g, 6 m²/g, or 7 m²/g, as measured by a nitrogen gas adsorption methodusing a BET analyzer. If the peak intensity ratio (B/A) of the zincoxide is less than about 0.01, the thermoplastic resin composition cansuffer from deterioration in antibacterial properties, and if the peakintensity ratio (B/A) of the zinc oxide exceeds about 1, thethermoplastic resin composition cannot secure discoloration resistance,low odor, and creep resistance. Further, if the BET surface area of thezinc oxide exceeds about 10 m²/g, the thermoplastic resin compositioncannot secure low odor and creep resistance.

The zinc oxide may have an average particle diameter of about 0.2 μm toabout 3 μm, specifically about 0.5 μm to about 3 μm, for example, 0.5μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3μm, 2.4 μm, 2.5 μm, 2.6 μm. 2.7 μm, 2.8 μm, 2.9 μm, or 3 μm, as measuredusing a particle analyzer (LS 13 320 Particle size Analyzer, BeckmanCoulter Inc.). Within this range, the thermoplastic resin compositioncan secure good external appearance.

The zinc oxide may have a peak position degree (2θ) in the range ofabout 35° to about 37° and a crystallite size of about 1,000 Å to about2,000 Å, specifically about 1,200 Å to about 1,800 Å, for example, 1,200Å, 1,300 Å, 1,400 Å, 1,500 Å, 1,600 Å, or 1,700 Å, in X-ray diffraction(XRD) analysis, as calculated by Equation 1. Within this range, thethermoplastic resin composition can have good properties in terms ofinitial color, weather resistance, antibacterial properties, and thelike.

$\begin{matrix}{{{{Crystallite}\mspace{14mu}{size}\mspace{14mu}(D)} = \frac{K\lambda}{\beta cos\theta}},} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

where K is a shape factor, λ is an X-ray wavelength, β is an FWHM value(degree) of an X-ray diffraction peak, and θ is a peak position degree.

In some embodiments, the zinc oxide may have a purity of about 99% ormore. Within this range, the thermoplastic resin composition can havefurther improved initial color, weather resistance, antibacterialproperties, and the like.

In some embodiments, the zinc oxide may be prepared by melting metalliczinc in a reactor, heating the molten zinc to about 850° C. to about1,000° C., specifically about 900° C. to about 950° C., to vaporize themolten zinc, injecting oxygen gas into the reactor, cooling the reactorto about 20° C. to about 30° C., heating the reactor to about 700° C. toabout 800° C. for about 30 min to about 150 min while injectingnitrogen/hydrogen gas into the reactor, as needed, and cooling thereactor to room temperature (about 20° C. to about 30° C.).

In some embodiments, the zinc oxide may be present in an amount of about0.1 parts by weight to about 10 parts by weight, specifically about 2parts by weight to about 6 parts by weight, for example, 2 parts byweight, 3 parts by weight, 4 parts by weight, 5 parts by weight, or 6parts by weight, relative to about 100 parts by weight of thethermoplastic resin (A). Within this range, the thermoplastic resincomposition can have good properties in terms of impact resistance,flame retardancy, low odor, and antibacterial properties.

In some embodiments, the (A3) α-methylstyrene copolymer and the (B) zincoxide may be present in a weight ratio of about 1.5:1 to about 15:1, forexample, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1,6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 10.5:1, 11:1, 11.5:1,12:1, 12.5:1, 13:1, 13.5:1, 14:1, 14.5:1, or 15:1. Within this range,the thermoplastic resin composition can have good properties in terms ofimpact resistance, flame retardancy, low odor, and antibacterialproperties.

According to one embodiment of the invention, the thermoplastic resincomposition may further include additives used in typical thermoplasticresin compositions. Examples of the additives may include flameretardants, fillers, antioxidants, anti-dripping agents, lubricants,release agents, nucleating agents, antistatic agents, stabilizers,pigments, dyes, and mixtures thereof, without being limited thereto. Theadditives may be present in an amount of about 0.001 parts by weight toabout 40 parts by weight, specifically about 0.1 parts by weight toabout 10 parts by weight, for example, 0.1 parts by weight, 1 parts byweight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 partsby weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9parts by weight, or 10 parts by weight, relative to 100 parts by weightof the thermoplastic resin.

According to one embodiment of the invention, the thermoplastic resincomposition may be prepared in pellet form by mixing the aforementionedcomponents, followed by melt extrusion using a typical twin-screwextruder at about 200° C. to about 280° C., specifically about 220° C.to about 250° C., for example, 220° C., 230° C., 240° C., or 250° C.

The thermoplastic resin composition exhibits antibacterial effectagainst various bacteria, such as Staphylococcus aureus, Escherichiacoli, Bacillus subtilis, Pseudomonas aeruginosa, salmonella,pneumococcus, and Methicillin-Resistant Staphylococcus aureus (MRSA).

In some embodiments, the thermoplastic resin composition may have anantibacterial activity against Staphylococcus aureus of about 2.0 toabout 7.0, specifically about 3 to about 7.0, more specifically about 4to about 6.5, for example, 4, 4.5, 5.5, 6, or 6.5, and an antibacterialactivity against Escherichia coli of about 2.0 to about 7.5,specifically about 4 to about 7.0, more specifically about 5 to about6.5, for example, 5.5, 6, or 6.5, as measured on 5 cm×5 cm specimensinoculated with Staphylococcus aureus and Escherichia coli,respectively, in accordance with JIS Z 2801 and calculated according toEquation 3.Antibacterial activity=log(M1/M2),  [Equation 3]

where M1 is the number of bacteria as measured on a blank specimen afterincubation under conditions of 35° C. and 90% RH for 24 hours and M2 isthe number of bacteria as measured on a specimen of the thermoplasticresin composition after incubation under conditions of 35° C. and 90% RHfor 24 hours.

The thermoplastic resin composition may have an impact strength of about18 kgf cm/cm or more, specifically about 18 kgf cm/cm to about 30 kgfcm/cm, for example, 18 kgf cm/cm, 19 kgf cm/cm, 20 kgf cm/cm, 21kgfcm/cm, 22 kgf cm/cm, 23 kgf cm/cm, 24 kgf cm/cm, 25 kgf cm/cm, 26 kgfcm/cm, 27 kgf cm/cm, 28 kgf·cm/cm, 29 kgf·cm/cm, or 30 kgf·cm/cm, asmeasured on a ⅛″ thick specimen in accordance with ASTMD256.

In some embodiments, the thermoplastic resin composition may have atotal volatile organic compound (TVOC) of about 1780 Area/g or less, forexample, about 0 to about 1775 Area/g, about 0 to about 1770 Area/g,about 0 to about 1735 Area/g, or about 0 to about 1700 Area/g, asmeasured by residual HS-GC at 120° C. for 5 hours.

The thermoplastic resin composition may have a creep displacement ofless than about 0.89 mm, for example, about 0 to about 0.88 mm, about 0to about 0.88 mm, about 0 to about 0.85 mm, or about 0 to about 0.82 mm,as measured under conditions of 60° C. and 150 N.

In some embodiments, the thermoplastic resin composition may have aVicat softening temperature (VST) of about 90° C. or more, for example,about 92° C. or more, about 94° C. or more, about 95° C. or more, orabout 96° C. or more, as measured on a ¼″ thick specimen under a load of5 kgf at 50° C./h in accordance with ISO 306B50. Although an upper Vicatsoftening temperature limit of the thermoplastic resin composition isnot particularly limited, the thermoplastic resin composition may have aVicat softening temperature (VST) of, for example, about 500° C. orless, or about 450° C. or less.

A molded article according to the present invention is produced from thethermoplastic resin composition. The thermoplastic resin composition maybe prepared in pellet form and the prepared pellets may be produced intovarious molded articles (products) by various molding methods, such asinjection molding, extrusion, vacuum molding, and casting. Such moldingmethods are well known to those skilled in the art. The molded articleshave good balance between impact strength, creep resistance, heatresistance, fluidity and antibacterial properties while exhibiting goodflame retardancy without adding a separate flame retardant, and thus maybe suitably applied to antibacterial products and exterior materials,for example, office equipment or household appliances, which entailfrequent body contact.

Next, the present invention will be described in more detail withreference to some examples. It should be understood that these examplesare provided for illustration only and are not to be in any wayconstrued as limiting the present invention.

EXAMPLE

(A) Thermoplastic Resin

(A1) Rubber-Modified Aromatic Vinyl Graft Copolymer

A g-ABS copolymer obtained by grafting 55 wt % of a mixture of styreneand acrylonitrile (weight ratio: 75/25) to 45 wt % of butadiene rubberparticles having a Z-average of 310 nm was used.

(A2) Aromatic Vinyl Copolymer Resin

A SAN copolymer having a melt index of 7 g/10 min as measured using aGottfert MI-3 in accordance with ASTM D 1238 and a weight averagemolecular weight of 100,000 g/mol and containing 30 wt % ofacrylonitrile was used.

(A3) α-Methylstyrene Copolymer

An AMS-SAN copolymer containing 30 wt % of acrylonitrile and having aweight average molecular weight of 150,000 g/mol was used.

(A4) Aromatic Vinyl Copolymer Resin

A SAN copolymer having a melt index of 2 g/10 min as measured byGottfert MI-3 in accordance with ASTM D 1238 and a weight averagemolecular weight of 100,000 g/mol and containing 30 wt % ofacrylonitrile was used.

(B) Zinc Oxide

Zinc oxide as listed in Table 1 was used.

TABLE 1 (B1) (B2) Average particle diameter (μm) 1.0 1.1 BET surfacearea (m²/g) 6 15 Purity (%) 99.2 97 PL peak intensity ratio (B/A) 0.059.8 Crystallite size (Å) 1229 503

Property Measurement of Zinc Oxide

(1) Average particle diameter (unit: μm): Average particle diameter(volume average) was measured using a particle analyzer (LaserDiffraction Particle Analyzer LS 13 320, Beckman Coulter Inc.).

(2) BET surface area (unit: m²/g): BET surface area was measured by anitrogen gas adsorption method using a BET analyzer (Surface Area andPorosity Analyzer ASAP 2020, Micromeritics Inc.).

(3) Purity (unit: %): Purity was measured by thermo-gravimetric analysis(TGA) based on the weight of the remaining material at 800° C.

(4) PL peak intensity ratio (B/A): Spectrum emitted upon irradiation ofa specimen using a He—Cd laser (KIMMON, 30 mW) at a wavelength of 325 nmat room temperature was detected by a CCD detector in aphotoluminescence measurement method, in which the CCD detector wasmaintained at −70° C. A peak intensity ratio (B/A) of peak A in thewavelength range of 370 nm to 390 nm to peak B in the wavelength rangeof 450 nm to 600 nm was measured. Here, an injection molded specimen wasirradiated with laser beams without separate treatment upon PL analysisand zinc oxide powder was compressed in a pelletizer having a diameterof 6 mm to prepare a flat specimen.

(5) Crystallite size (unit: A): Crystallite size was measured using ahigh-resolution X-ray diffractometer (PRO-MRD, X'pert Inc.) at a peakposition degree (2θ) in the range of 35° to 37° and calculated byScherrer's Equation (Equation 1) with reference to a measured FWHM value(full width at half maximum of a diffraction peak). Here, both aspecimen in powder form and an injection molded specimen could be used,and for more accurate analysis, the injection molded specimen wassubjected to heat treatment at 600° C. in air for 2 hours to remove apolymer resin before XRD analysis.

$\begin{matrix}{{{{Crystallite}\mspace{14mu}{size}\mspace{14mu}(D)} = \frac{K\lambda}{\beta cos\theta}},} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

where K is a shape factor, λ is an X-ray wavelength, θ is an FWHM value(degree) of an X-ray diffraction peak, and θ is a peak position degree.

Examples 1 to 3 and Comparative Examples 1 to 5: Preparation ofThermoplastic Resin Composition

The above components were placed in amounts as listed in Tables 2 and 3and subjected to extrusion at 230° C., thereby preparing pellets.Extrusion was performed using a twin-screw extruder (L/D=36, Φ: 45 mm).The prepared pellets were dried at 80° C. for 4 hours or more andinjection-molded in a 6 oz. injection molding machine (moldingtemperature: 250° C., mold temperature: 60° C.), thereby preparingspecimens. The prepared specimens were evaluated as to the followingproperties by the following method, and results are shown in Table 2.

Property Evaluation

(1) Antibacterial activity: Antibacterial activity was measured on 5cm×5 cm specimens inoculated with Staphylococcus aureus and Escherichiacoli, respectively, in accordance with JIS Z 2801 and calculated byEquation 3.Antibacterial activity=log(M1/M2),  [Equation 3]

where M1 is the number of bacteria as measured on a blank specimen afterincubation under conditions of 35° C. and 90% RH for 24 hours and M2 isthe number of bacteria as measured on a specimen of the foam afterincubation under conditions of 35° C. and 90% RH for 24 hours.

(2) Impact strength (unit: kgf·cm/cm): Impact strength was measured on a⅛″ thick specimen using an INSTRON instrument in accordance withASTMD256.

(3) Low odor (unit: Area/g): Total volatile organic compound (TVOC) wasmeasured at 120° C. for 5 hours using HS-GC.

(4) Creep displacement (unit: mm): Displacement of a specimen wasmeasured using a creep tester (Yonekura MFG Co., Ltd.) under conditionsof 60° C. and 150 N. A lower displacement of the specimen indicatesbetter creep resistance.

(5) Flame retardancy: Flame retardancy was measured under UL 94 5Vconditions (125 mm Vertical Burning Test).

(6) Fluidity (unit: g/10 min): Melt index (MI) was measured using aGottfert MI-3 under conditions of 200° C. and 5 kg in accordance withASTM D1238.

(7) Heat resistance (unit: ° C.): Vicat softening temperature (VST) wasmeasured under conditions of 5 kgf and 50° C./h on a ¼″ thick specimenusing in accordance with ISO 306B50.

TABLE 2 Example 1 Example 2 Example 3 (A) (A1) 26 26 26 (A2) 69 69 64(A3) 5 5 10 (A4) — — — (B) (B1) 2 3 2 Antibacterial Staphylococcus 4.55.8 5.1 activity aureus Escherichia 3.2 4.0 3.5 coli Impact strength(kgf · cm/cm) 22 18 20 Low odor (Area/g) 1,771 1,699 1,732 Creepresistance (mm) 0.88 0.85 0.82 Flame retardancy V-2 V-2 V-2 Fluidity(g/10 min) 7.5 6.8 6.5 VST (° C.) 94.5 95.6 96.2

TABLE 3 Comparative Comparative Comparative Comparative ComparativeExample 1 Example 2 Example 3 Example 4 Example 5 (A) (A1) 26 26 26 2626 (A2) 69 — 69 69 69 (A3) — 5 5 5 5 (A4) 5 69 — — — (B) (B1) 2 2 — 200.01 (B2) — — 2 — — Antibacterial Staphylococcus 5.5 6.2 5.9 6.8 1.2activity aureus Escherichia 3.8 3.9 4.6 5.7 0.5 coli Impact strength(kgf · cm/cm) 21 20 10 2 24 Low odor (Area/g) 1,781 1,812 2,008 1,5532,195 Creep resistance (mm) 1.00 0.85 0.89 0.79 0.90 Flame retardancyV-2 Fail V-2 Fail V-2 Fluidity (g/10 min) 7.9 1.8 7.3 3.1 7.9 VST (° C.)90.5 95.8 94.5 95.2 94.9

In the above results, the thermoplastic resin compositions of Examples 1to 3 exhibited good properties in terms of low odor, impact strength,creep resistance, flame retardancy, fluidity, heat resistance, andantibacterial properties. Conversely, the thermoplastic resincomposition of Comparative Example 1 prepared using a typical SANcopolymer instead of an α-methylstyrene copolymer exhibiteddeterioration in heat resistance and creep resistance, the thermoplasticresin composition of Comparative Example 2 prepared using a typical SANcopolymer instead of a SAN copolymer having a high melt index sufferedfrom deterioration in fluidity and had no flame retardancy. Thethermoplastic resin composition of Comparative Example 3 prepared usingzinc oxide instead of zinc oxide according to the present inventionexhibited antibacterial properties and suffered from deterioration inimpact strength and low odor. In addition, the thermoplastic resincomposition of Comparative Example 4 prepared using an excess of zincoxide suffered from deterioration in impact strength, fluidity and flameretardancy, and the thermoplastic resin composition of ComparativeExample 7 prepared using a smaller amount of zinc oxide exhibiteddeterioration in low odor and antibacterial properties.

It should be understood that various modifications, changes,alterations, and equivalent embodiments can be made by those skilled inthe art without departing from the spirit and scope of the presentinvention.

The invention claimed is:
 1. A thermoplastic resin compositioncomprising: 100 parts by weight of (A) a thermoplastic resin comprising(A1) a rubber-modified aromatic vinyl graft copolymer, (A2) an aromaticvinyl copolymer resin having a melt index (MI) of about 5 g/10 min toabout 8 g/10 min, as measured in accordance with ASTM D 1238, and (A3)an α-methylstyrene copolymer; and about 0.1 parts by weight to about 10parts by weight of (B) zinc oxide, wherein the zinc oxide has a peakintensity ratio (B/A) of about 0.01 to about 1, where A indicates a peakin the wavelength range of 370 nm to 390 nm and B indicates a peak inthe wavelength range of 450 nm to 600 nm in photoluminescencemeasurement, a BET surface area of about 10 m²/g or less, as measuredusing a BET analyzer, a peak position (2θ) in the range of 35° to 37° inX-ray diffraction (XRD) analysis and a crystallite size of about 1,000 Åto about 2,000 Å, as calculated by Equation 2: $\begin{matrix}{{{{Crystallite}\mspace{14mu}{size}\mspace{14mu}(D)} = \frac{K\lambda}{\beta cos\theta}},} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$ where K is a shape factor, λ is an X-ray wavelength, β isan FWHM value (degree) of an X-ray diffraction peak, and θ is a peakposition degree.
 2. The thermoplastic resin composition according toclaim 1, wherein the (A2) aromatic vinyl copolymer resin has a weightaverage molecular weight of about 85,000 g/mol to about 150,000 g/mol.3. The thermoplastic resin composition according to claim 1, wherein the(A3) α-methylstyrene copolymer is a copolymer of about 65 wt % to about80 wt % of α-methylstyrene and about 20 wt % to about 35 wt % ofacrylonitrile.
 4. The thermoplastic resin composition according to claim1, wherein the (A3) α-methylstyrene copolymer has a weight averagemolecular weight of about 130,000 g/mol to about 180,000 g/mol.
 5. Thethermoplastic resin composition according to claim 1, wherein thethermoplastic resin composition satisfies Equation 1:M _(A2) <M _(A3),  [Equation 1] where M_(A2) is the weight averagemolecular weight of the (A2) aromatic vinyl copolymer resin and M_(A3)is the weight average molecular weight of the (A3) α-methylstyrenecopolymer.
 6. The thermoplastic resin composition according to claim 1,wherein the (A2) aromatic vinyl copolymer resin and the (A3)α-methylstyrene copolymer are present in a weight ratio ((A2):(A3)) ofabout 5:1 to about 15:1.
 7. The thermoplastic resin compositionaccording to claim 1, wherein the (A) thermoplastic resin comprisesabout 20 wt % to about 45 wt % of the (A1) rubber-modified aromaticvinyl graft copolymer; about 40 wt % to about 75 wt % of the (A2)aromatic vinyl copolymer resin; and about 3 wt % to about 15 wt % of the(A3) α-methylstyrene copolymer.
 8. The thermoplastic resin compositionaccording to claim 1, wherein the zinc oxide has an average particlediameter (D50) of about 0.2 μm to about 3 μm.
 9. The thermoplastic resincomposition according to claim 1, wherein the zinc oxide has a peakintensity ratio (B/A) of about 0.01 to about 0.5, where A indicates apeak in the wavelength range of 370 nm to 390 nm and B indicates a peakin the wavelength range of 450 nm to 600 nm in measurement ofphotoluminescence.
 10. The thermoplastic resin composition according toclaim 1, wherein the (A3) α-methylstyrene copolymer and the (B) zincoxide are present in a weight ratio of about 1.5:1 to about 15:1. 11.The thermoplastic resin composition according to claim 1, wherein thethermoplastic resin composition has a total volatile organic compound(TVOC) of about 1,780 Area/g or less at 120° C. for 5 hours, an impactstrength of about 18 kgf·cm/cm or more, as measured on a ⅛″ thickspecimen in accordance with ASTMD256, and an antibacterial activityagainst Staphylococcus aureus of about 2.0 to about 7.0 and anantibacterial activity against Escherichia coli of about 2.0 to about7.5, as measured on 5 cm×5 cm specimens inoculated with Staphylococcusaureus and Escherichia coli, respectively, in accordance with JIS Z 2801and calculated according to Equation 3:Antibacterial activity=log(M1/M2),  [Equation 3] wherein M1 is thenumber of bacteria as measured on a blank specimen after incubationunder conditions of 35° C. and 90% RH for 24 hours, and M2 is the numberof bacteria as measured on a specimen of the thermoplastic resincomposition after incubation under conditions of 35° C. and 90% RH for24 hours.
 12. A molded article produced from the thermoplastic resincomposition according to claim 1.